1. Field of the Invention
The present invention relates to a zoom lens system, and specifically relates to a zoom lens system capable of high variable magnification using few lens elements, and an optical construction suitable for digital still cameras, silver halide cameras, video cameras and television cameras. for example.
2. Description of the Related Art
On one hand, in recent years demand has grown for compact and inexpensive video cameras and television cameras, and there has been an accompanying demand for compact and inexpensive photographic lens systems for use with such cameras. On the other hand, there is increasing demand for higher specification products, including zoom lens systems of high variable magnification for use as photographic lens systems. Although the demand for compact, inexpensive, high variable magnification optical systems is contradictory, response to said demand has led to various improvements in zoom lens systems.
For example, Japanese Laid-Open Patent Application Nos. 2-56515, 4-281419, and 5-203875 and U.S. Pat. No. 5,543,970 respectively disclose three-component zoom lens systems comprising sequentially from the object side a positive first lens unit, negative second lens unit, and positive third lens unit as zoom lens systems which are compact and inexpensive while providing high variable magnification.
The zoom lens systems of the aforesaid disclosures leave room for improvement in the overall length of the total lens system, and number of lens elements. Also, zoom lens systems which utilize few lens elements have not been responsive to the aforesaid demanded specifications insofar as their magnification ratio is only 2.times.-3.times..